Catalysts for oxygen and hydrogen evolution reactions (OER/HER) are the heart of renewable green energy source like water splitting. Although incredible efforts have been done to develop catalysts for OER and HER with good efficiency but still great challenges remain to come up with single bi-functional catalysts. Here, we report a novel hybrid of Co3O4 embedded in tubular nanostructures of graphitic carbon nitride (GCN) synthesized through a facile and large scale chemical method at low temperature. Strong synergistic effect among Co3O4 and GCN results in excellent performance as a bi-functional catalyst for OER and HER. High surface area, unique tubular nanostructure and composition of the hybrid bring all redox sites easily available for catalysis and provide faster ionic and electronic conduction. The Co3O4@GCN tubular nanostructured (TNS) hybrid exhibits the lowest over potential (0.12 V) and excellent current density (147 mAcm-2) for OER, better than benchmark IrO2 and RuO2, with superior durability in alkaline media. Furthermore, the Co3O4@GCN TNS hybrid demonstrates excellent performance for HER with much lower onset and over potential as well as stable current density. It is expected that the Co3O4@GCN TNS hybrid developed in the present study is an attractive alternative catalyst than noble metals for large scale water splitting and fuel cells.